Field of the Invention
The present invention relates to an image forming device which transfers a toner image formed on an image carrier to a transferred body and removing a residual material on the image carrier after the transfer by means of a cleaning blade.
Description of the Related Art
An image forming device such as an electrophotographic printer includes an intermediate transfer system which forms toner images of respective colors of Y (yellow), M (magenta), C (cyan) and K (black) on respective photoreceptor drums and overlaps the toner images of Y to K colors formed on the respective photoreceptor drums with a rotating intermediate transfer belt to primarily transfer, then secondarily transfers the toner images of the respective colors multi-transferred to the intermediate transfer belt to a recording sheet, for example.
A belt formed of a resin material such as PI (polyimide) and PPS (polyphenylenesulfide) is generally widely adopted as such intermediate transfer belt, but there is a case in which adhesiveness in a secondary transfer position between the intermediate transfer belt and the recording sheet is deteriorated due to difference in macroscopic unevenness of a surface shape among paper types to be used (for example, normal paper, thin coated paper, thick paper and the like) and it becomes difficult to secure a transfer property.
In order to prevent such deterioration in the transfer property, there is a configuration in which an elastic layer made of a rubber material and the like is provided on a base layer made of the resin material on the intermediate transfer belt to make a surface shape of the intermediate transfer belt deformable to fit a surface shape of the recording sheet by the elastic layer, such that the adhesiveness between the intermediate transfer belt and the recording sheet is improved.
When the toner image on the intermediate transfer belt is transferred to the recording sheet, all the toner images are ideally transferred to the recording sheet; however, there actually is a case in which a part of toner particles remains on the intermediate transfer belt without being transferred. There also is a case in which paper powder adheres to the intermediate transfer belt by contact with the recording sheet. If such a residual material such as the remained toner and paper powder remains adhering to the intermediate transfer belt, this causes a trouble in subsequent formation of the toner image, so that a cleaner which removes the residual material on the intermediate transfer belt is provided.
As the above-described cleaner, a configuration of allowing a tip end of the cleaning blade made of an elastic body such as urethane rubber to abut a rotating intermediate transfer belt and scrapping the residual material on the intermediate transfer belt to remove is common.
In a configuration in which the cleaning blade formed of the elastic body abuts the intermediate transfer belt including the elastic layer, a real contact area becomes larger by abutment between the elastic bodies and frictional force generated between contacting portions becomes significantly large. Therefore, abrasion of the cleaning blade or the intermediate transfer belt is promoted and a lifetime becomes problematically short.
When hardness of the elastic body such as urethane rubber being a material of the cleaning blade changes by change in peripheral temperature, for example, a contact area between the intermediate transfer belt and the cleaning blade varies and the frictional force between the intermediate transfer belt and the cleaning blade also varies. The frictional force acts as brake to the rotating intermediate transfer belt, so that a rotational speed of the intermediate transfer belt varies due to increased variation in the frictional force, that is to say, brake force and peripheral speed difference occurs between the same and each photoreceptor drum rotating at a certain speed.
When the peripheral speed difference between the intermediate transfer belt and each photoreceptor drum occurs, positions of the toner images of respective colors transferred to the intermediate transfer belt easily displace to each other in a rotational direction when the toner images of respective colors are multi-transferred from the photoreceptor drums to the intermediate transfer belt. This displacement is problematic because color shift occurs when a color image is formed.
The above-described problem is not limited to the configuration of transferring the toner image on the intermediate transfer belt to the recording sheet. For example, this might generally occur in a configuration of transferring the toner image on an image carrier to a transferred body such as a configuration of transferring the toner image formed on a photoreceptor belt to an intermediate transfer drum.